Surface plasmon resonance (SPR) measurement systems rely on surface plasmon resonances to detect changes in refractive index of a target at a transducing interface. Due to the surface plasmon resonance phenomenon, optical signals that are incident on the transducing interface undergo a loss at a resonant incidence angle. Changes in the refractive index of the target cause changes in the resonant incidence angle that can be detected by measurements of the intensity of optical signals that are deflected by the target. An SPR measurement system relates detected changes in the resonant incidence angle to corresponding changes in the refractive index of the target, typically in the form of an SPR sensorgram, which is a plot of the relative refractive index of the sample versus time. SPR sensorgrams can be used to characterize biochemical processes at the transducing interface based on relationships between the biochemical processes and refractive indices of the targets at the transducing interface.
A prior art SPR measurement system (shown in FIG. 1) detects shifts in resonant incidence angle by measuring the intensity of the optical signals deflected by the target while mechanical actuators rotate the target over an angular adjustment range +/−2.5 degrees to vary the incidence angle of the target relative to an incident optical beam. Because some biochemical processes can produce shifts in resonant incidence angle of less than 10−4 degrees, it may be desirable for the SPR measurement system to have capability to measure small shifts in resonant incidence angle that are induced by changes in refractive index. In addition, it may be desirable for angular rotation of the target to occur at high repetition rates to detect biochemical processes of short duration at the transducing interface. However, the precision of the measurements of the resonant incidence angle, and the repetition rates for detecting biochemical processes at the transducing interface are limited by the mechanical actuators used in the SPR measurement system to provide the angular rotations of the target.